It seems that, in association with development and diffusion of network environment, a network system in which a plurality of workstations are connected to each other through a network will become more advanced and more sophisticated.
Resources shared by workstations connected to each other in a network system are called server, and generally such servers as a file server providing dedicated services for construction of more efficient systems by sharing a large scale file, a communication server in which communicating functions for communications with other network systems (or computer systems) through a wide area network are concentrated, and furthermore a print server providing dedicated controls over output devices for use of output devices such as printers are known.
On the other hand, as I/O devices, such devices as, for instance, a printer providing a luster image as output to record paper, a scanner reading a manuscript as a luster image, a modem executing data transactions with external systems making use of a telephone network, and a console which is a man machine interfacing means between users and a machine (a workstation) are known.
Types of data transferred between these I/O devices are classified to image data, character data, and graphic data. However, there are various restrictions concerning the way to express each type of data, and practically there are many types of data. Also there are may types of I/O device because of difference in such factors as resolution and tone.
For the reasons as described above, in I/O devices connected to the conventional type of network system (or in I/O devices which may be connected to the conventional type of network in the future), a convertor to convert data is installed so that any type of data can be processed in the network system.
However, there have been the problems (1) to (5) as described hereinafter in the conventional type of network system.
(1) When a print server is used, although a printer connected to a network can be shared by each workstation, the system generally assumes use of a printer by a plurality of users, so that the printer can not be used so conveniently and freely as a printer dedicated for use in each individual workstation. Concretely, as operating environment for each individual user can not be maintained, printer setting changes each time any other user uses the printer. Also output from a number of users is provided to the same printer, management of record paper (output paper) becomes complicated and it is hard to insure security of output data.
(2) Also in a case where a system having a new functions such as, for instance, a printing system enabling data output to a shared printer from a plurality of workstations is added to a network system already installed, sometimes it is required to make an additional investment to introduce new network environment or facilities, or to change I/O devices already installed to new ones, so that it is very difficult to carry out system expansion or addition of new functions.
(3) As data type for I/O devices is converted to one corresponding to a network system so that the data can be transacted in the network system by incorporating a convertor in each I/O device, when a network system is introduced anew, if a convertor already installed in an I/O device can not correspond to the need for data conversion (or if the converted can not be integrated with the network system), then a new convertor must be added, or the converted already installed must be modified, or even a new I/O device must be purchased to satisfy the needs for the network system to be introduced anew.
(4) Development of I/O devices is made on the condition that, when an I/O device is connected to a network system, requirements for data type in the network are satisfied by incorporating a convertor in the I/O device, so that, as functions of the I/O device become more sophisticated, a vast amount of cost and time is required for designing and evaluating the convertor.
(5) Also in an optimized network system, as system development and development (or selection) of I/O devices required for the network system are carried out simultaneously, it is difficult to expand the system by adding I/O devices each based on different specifications. This problem in turn causes a great loss in the side of users in recent business environment where advanced and high value-added products have been developed and put into the market one after another.